Squares, by definition, have all four interior angles equal and each is a right angle.
Therefore, the angles of a square are all 90 degrees.
This is because a square is a specific type of rectangle where all four sides are equal, and opposite sides are parallel. Since parallel lines are cut by a transversal (in this case, an imaginary line extending one side of the square) and the alternate interior angles are congruent, these angles in a square will each measure 90 degrees.